Ancistrorhynchus tenuicaulis Summerh., Kew Bull. 8: 590 (1953 publ. 1954).
Plants with erect or curved stems, 2–16 cm high, 2 mm in diameter, with few narrow roots, 1–2 mm in diameter. Leaves linear, clustered near apex of stem, unequally bilobed at the apex, each lobe subacute or obscurely 2-toothed, articulated to rugulose leaf bases, 2–7.2 cm long, 4–5 mm wide. Inflorescences capitate, dense, 4–5 mm long, many-flowered; bracts elliptic, obtuse, 2–3 mm long; pedicel with ovary 3 mm long. Flowers white; dorsal sepal oblong-elliptic, rounded, 1.5–3.5 mm long, 0.9–1.3 mm wide; lateral sepals obliquely elliptic-oblong, obtuse, 2–3.5 mm long, 1–1.2 mm wide; petals elliptic, rounded, 1.7–3 mm long, 0.7–1.4 mm wide; lip concave, ovate, obtuse, 1.4–2.5 mm long, 1.4–2.4 mm wide; spur globose or club-shaped, 1–2 mm long.
Epiphyte in lowland and submontane primary forest. In Rio Muni, specimens were also collected in the forest fringe of an inselberg. Altitudinal range from 400 to 1200 m. Flowering peaks between May and July.
As given for the genus, warm to cool growing epiphyte.
This is one of the small-flowered species, somewhat similar to Ancistrorhynchus parviflorus in Tanzania and to Ancistrorhynchus schumannii and Ancistrorhynchus straussii from west and central.
Gabon to Uganda and Malawi
Flora of Tropical East Africa Orchidaceae Cribb 1989; Angraecoid Orchids Stewart, Hermans and Campbell 2006; WCSP (2017). 'World Checklist of Selected Plant Families. 10.03-2017; http://apps.kew.org/wcsp/
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